1、,Can You Measure It?,Planning a Successful “Round Robin”,Paul Schiffelbein ASTM Committee Week14 June 2006,Overview,Measurement system analysis (Round robin, Interlaboratory Study (ILS), Interlaboratory Comparison (ILC), Gage Study) description, definitions and motivationRound robin guidelinesRound
2、robin logisticsData AnalysisPrecision and bias statement,Purpose of Measurement System Analysis,Ensure the measurement system has adequate accuracy: precision and biasIdentify sources of measurement variation (and make improvements, if necessary)Compare several test devices, test methodologies, test
3、 locations (linearity, bias, sensitivity)Quantify measurement variability for reference,Actual Process Variation,Measurement Variation,Observed Process Variation,Long-term Process Variation,Short-term Process Variation,Variation within a Sample,Variation due to Labs, Operators, Devices, Time,Variati
4、on due to Gage,Bias,Linearity,“Short-term”,Stability,“Long-term”,Measurement Process Variation,Simple,“precision”,“bias”,ISO 5725-1, ASTM E177,Accuracy: The closeness of agreement between a test result and the accepted reference value“Accuracy,” when applied to a set of test results, involves a comb
5、ination of random components and a common systematic error or bias componentBias: the difference between the expectation of test results and an accepted reference valueBias is the total systematic error as contrasted to random error. There may be one or more systematic components contributing to the
6、 bias.,ISO 5725-1, ASTM E177,Precision: The closeness of agreement between independent test results obtained under stipulated conditions.Precision depends only on the distribution of random errors and does not relate to the true value or the specified value.Precision can be decomposed into short- an
7、d long-term (or narrow and wide) components. Repeatability and reproducibility are used to quantify this concept.,ISO 5725-1,Repeatability: Precision under repeatability conditionsindependent test results the same test method identical test items the same laboratory the same operator the same equipm
8、ent within short time intervalRepeatability standard deviation: The standard deviation of test results obtained under repeatability conditionsRepeatability limit (“r”): the absolute difference between two test results obtained under repeatability conditions should be less than or equal to this value
9、,ISO 5725-1,Reproducibility: Precision under reproducibility conditionsindependent test results the same test method identical test items different laboratories different operators different equipment longer time intervalReproducibility standard deviation: The standard deviation of test results obta
10、ined under reproducibility conditionsReproducibility limit (“R”): the absolute difference between two test results obtained under reproducibility conditions should be less than or equal to this value,Actual Process Variation,Measurement Variation,Observed Process Variation,Long-term Process Variatio
11、n,Short-term Process Variation,Variation within a Sample,Variation due to Labs, Operators, Devices, Time,Variation due to Gage,Bias,Linearity,“Short-term” “repeatability”,Stability,“Long-term”,ASTM/ISO Usage,Simple,“reproducibility”,“bias”,Actual Process Variation,Measurement Variation,Observed Proc
12、ess Variation,Long-term Process Variation,Short-term Process Variation,Variation within a Sample,Variation due to Labs, Operators, Devices, Time,Variation due to Gage,Bias,Linearity,“Short-term” “repeatability”,Stability,“Long-term” “reproducibility”,Gage R&R/Auto Industries Usage,Simple,“Gage”,“bia
13、s”,Round Robin Guidelines,E 691 “Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method”D 2904 “Standard Practice for Interlaboratory Testing of a Textile Test Method that Produces Normally Distributed Data”,Round Robin Guidelines,The design should be a
14、s simple as possible in order to obtain estimates of within- and between-laboratory variability that are free of secondary effects Study should include a minimum of five laboratories A minimum of two operators should be used per laboratory When multiple instruments within a laboratory are used, test
15、s must be made on all equipment to establish the presence or absence of the equipment effect.,Logistics: D 885 Case Study,Motivation: The current version of D 885 was written for traditional tensile testing machines. Automated tensile testers are now being used in high-tenacity fiber testing, and ne
16、ed to be included in this standard. The current study will include three types of automated testers, as well as parallel testing on traditional tensile test devices. The objective of this study is to quantify test precision of traditional and automated testers, as well as any bias seen between the d
17、evice types. The study will only address aramid materials.,Logistics: D 885 Case Study,Responsibility: Task group D13.19 (Tire Cord and Fabrics) has overall responsibility of the ILS. Dawn Caullwine (chair) will act as overall coordinator for conducting the ILS. The coordinator will supervise the di
18、stribution of materials and protocols to the laboratories and receive the test result reports from the laboratories.,Logistics: D 885 Case Study,Study Design: Nine materials will be tested on each of three types of automated tensile test devices. Two devices of each type will be used. Yarn will be s
19、upplied in pre-twisted state for testing. Untwisted yarn will also be provided to Statimat labs, so testing can be performed both on pre-twisted yarn, and yarn automatically twisted by the test machine. Two laboratories will also test the materials using traditional methods for reference. Each of th
20、ose laboratories will use two operators.,Logistics: D 885 Case Study,Logistics: D 885 Case Study,Materials: The ILS will include the following nine materials (All samples are shipped twisted and ready to test, except for Statimat laboratories, which receive both twisted and untwisted samples): Kevla
21、r: 195 denier Kevlar: 600 denier Kevlar: 1140 denier Nomex: 200 denier Nomex: 1600 denier Technora: 550 denier Twaron: 840 denier Twaron: 1500 denier Twaron: 3000 denier,Logistics: D 885 Case Study,Test Determinations and Test Results: The number of test determinations required for a test result is
22、specified in each individual test method. For the purpose of this study, each laboratory will make one hundred (100) determinations (breaks) for each material.,Logistics: D 885 Case Study,Test Determinations and Test Results: The following properties (and associated measurement units) will be record
23、ed: Break strength (BS) N Elongation at break (EB) % Modulus between 300 mN/tex and 400 mN/tex (MOD) CN/tex FASE 0.3% N FASE 0.5% N FASE 1.0% N Use nominal linear density for modulus calculation.,Logistics: D 885 Case Study,Details: The test method being studied is D885-03. Specify the type of equip
24、ment used, including manufacturer, model, and software program. Samples should be conditioned as per D885 7.1 to moisture equilibrium in an environmentally controlled room for a minimum of 16 hours, at RH 55 +/- 2% and temperature 24 +/- 1 degrees C (72 +/- 2 degrees F). Specific for Para-Aramid: Ga
25、uge length: 500mm Crosshead rate: 250mm/min. (50%),Etc.,Logistics: D 885 Case Study,Data: Data should be entered into the Excel workbook provided. Label the workbook with your laboratory name, fill in the test data, and send the completed file to:Paul SchiffelbeinDuPont Engineering, Quality Manageme
26、nt & T302/774-2417,Logistics: D 885 Case Study,Logistics: D 885 Case Study,A Better Way?: Internet Entry for F 2130 RR,Figure courtesy of Dr. Anugrah Shaw, UMES,Data Structure Guaranteed!,Logistics: D 885 Case Study,Data Analysis:,Logistics: D 885 Case Study,Data Analysis:,Repeatability and Reproduc
27、ibility,Use between- and within-laboratory variance components:sR = s2L + s2rWhere:sR is the reproducibility standard deviation sr is the repeatability standard deviationsL is the square root of the inter-laboratory(device, operator, etc.) variance component,Logistics: D 885 Case Study,Data Analysis
28、:,Repeatability variance,Reproducibility variance (one estimate),Reproducibility variance (another estimate),Logistics: D 885 Case Study,Precision and Bias Statement:,Logistics: D 885 Case Study,Precision and Bias Statement:,Logistics: D 885 Case Study,Precision and Bias Statement:,Logistics: D 885
29、Case Study,Precision and Bias Statement:,Logistics: D 885 Case Study,Precision and Bias Statement:,Summary,Explicitly state objectives for your study, and make sure all participants understand them Write protocol covering responsibilities, timing, samples and sample handling, test equipment and set-up, sampling plan, properties, units, etc. Details are important! Be specific, explicit, and discuss ahead of time with task group to avoid surprises. Communicate! Set up data collection to be as “goof proof” as possible, and to facilitate subsequent analysis,Thank you,
